Does anyone know if its possible to add a couple of other users or create separate accounts that are partitioned somehow in Quicken 2005?

Yes, you can set up many checking accounts and Investment Accounts in a Quicken file, however if you are managing accounts for others I would suggest setting them up in a seperate file. I am Representative Payee for my daughter's Social Security Disability Check and I started by putting her checking account in my file, however I found it would be better for doing reports etc that each individual have a seperate file. Also, for Scheduled Transactions its better for each individual to have their own file. All of my accounts-checking, savings, investments, IRAs etc are in a file with my last name. My daughter's accounts are in a file with her first name. I can switch from one to the other by clicking on the word "File" in the uppermost left hand corner of the screen. At the bottom of the menu that comes down you will note the names of the last 4 files that you have been in. Just click on the file you want to work in.

Here's what I've done WRT investment accounts:I've created a Quicken file for each tax entity we have, including tax-deferrals. One file for retirement plans in my name/SSN, a separate file for retirement plans in my wife's name/SSN, one for all our taxable investments and one for our savings and emergency funds. While my father was alive I had an account for his investments as well. My way may appear awkward to those who like everything in one box so they can generate reports or see it all at once, but this way works well for me.